The National Institute of Allergy and Infectious Diseases (NIAID) supports a comprehensive portfolio of contract resources to discover and develop novel therapeutic agents for the prevention and treatment of infections caused by Human Immunodeficiency Virus-1 (HIV-1), AIDS-associated opportunistic pathogens, and other infectious agents. Animal model resources constitute one element of this drug discovery and development program. The purpose of the present project is to provide a resource for evaluating potential therapeutics for HIV-1 infection. Details regarding access by the scientific community are provided at: http://www.niaid.nih.gov/daids/pdatguide/overview.htm The contractor is responsible for i) evaluating therapeutic agents, alone and in combination, for efficacy and toxicity in vitro and in the SCID-hu thymus/liver animal model; ii) performing quality assurance/control of the components of the in vitro and in vivo assay systems, to insure reproducible evaluation of candidate therapies; iii) determining optimal routes and schedules of administration; iv) modifying the model system as necessary, to augment its usefulness for evaluating potential HIV-1 therapeutics; and 5) preparing and submitting periodic and interim reports.